1. Field of the Invention
The present invention relates to an indicating device mounted on a rotatable wheel for indicating the rotation of the wheel. The typical application of the device is as an indicator attached to the steering wheel of a car or a boat to show the turned direction of the car wheel or the rudder of the boat.
2. Description of the Related Art
U.S. Pat. No. 2,957,442 discloses an indicator settled at an off-steering wheel position where a cable transmits actuating motion to the indicator from a sector shaft connected with the steering shaft. Such an arrangement is unnecessarily complicated.
In U.S. Pat. No. 3,673,561 an indicator is disclosed which has gears which transmit rotation of the steering shaft to operate two variable resistance means that actuate an indicating meter and two lights. Such a device requires an electric power supply and the mounting of the gears is bothersome.
A device mainly including a planetary gear train mounted between a steering shaft and a bulkhead where the shaft rotatably passes through is disclosed in U.S. Pat. No. 4,013,034. A pinion (sun) gear is fixedly mounted on the shaft, and a hub furnished with an inner ring gear surrounds the pinion gear and is fixed to the bulkhead. A disc carrying an idler (planet) gear which meshes with the pinion gear, and the ring gear, gets a differential rotation corresponding to the rotation of the steering shaft relative to the hub. The fact that this device should be mounted around the shaft and occupies a space between the steering wheel and the bulkhead limits its application.
An ideal device would have a simple structure as an unit and could be built-in or attached on the steering wheel. This feature is taught in U.S. Pat. No. 3,569,932 and U.S. Pat. No. 4,157,076. Such indicators utilize a member having one or two spiral paths thereon secured to the steering wheel and a gravity-responsive member freely moving along the path(s) to show the rotation of the steering wheel by the particular position of the gravity-responsive member on that path. These indicators are not easy to read since they fail to provide a pointer means that directly indicates the left and right rotation, therefore making reading more difficult.